1. Field
Exemplary embodiments relate to a method of acquiring a horizontal distance between a camera and a target, and a camera and surveillance system using the method. In particularly, exemplary embodiments relate to a method of acquiring a horizontal distance between a central point of an optical system of a camera and a ground landing point of a target, and a camera and surveillance system adopting the method.
2. Description of the Related Art
In a related art, a host device of a camera or a surveillance system may need to acquire and display a distance between the camera and a target.
For example, in the related art, when the surveillance system is in operation and several cameras function simultaneously to trace a target, such as a person or a car, a distance between a camera that is currently photographing the target and the target, needs to be displayed.
In the related art, in order to acquire the distance between the camera and the target, a laser sensor or two or more adjacent cameras has been used.
In the related art, when a camera includes a laser sensor, the distance between the camera and the target is equal to the return speed of a laser beam, multiplied by the return time. However, this method of the related art has the following problems:
First, additional costs are generated in order to include a laser sensor in a camera.
Second, a straight line distance, not a horizontal distance, between the camera and the target is acquired. Thus, in the related art, it is difficult to know the horizontal distance between the camera and the target.
Further, a related art method of acquiring a distance between a camera and a target by using two or more adjacent cameras has the following problems:
First, only one camera in one area is used to take pictures of a target to obtain moving pictures thereof. Thus, the costs for the additional cameras are wasted.
Second, as images from two or more adjacent cameras are used, a method of calculating a distance between the camera and the target becomes complicated. In other words, an inaccurate result may be generated, due to calculation delay. For example, it may be difficult to accurately display in real time the distance between a car moving at a fast speed and a camera.
Accordingly, there is a need for a method of acquiring a horizontal distance between a central point of an optical system of a camera and a ground landing area of a target, and a camera and surveillance system adopting the method